@InProceedings{DoyleBarr:2006:ReENPh,
               author = "Doyle, Moira and Barros, Vicente",
          affiliation = "Departamento de Ciencias de la Atm{\'o}sfera y los 
                         Oc{\'e}anos,UBA, CIMA-CONICET, Ciudad Universitaria, 
                         Pabell{\'o}n II, 2do piso, 1428, Buenos Aires, Argentina",
                title = "Precipitation trends in southeastern South America: relationship 
                         with ENSO phases",
            booktitle = "Proceedings...",
                 year = "2006",
               editor = "Vera, Carolina and Nobre, Carlos",
                pages = "1513--1517",
         organization = "International Conference on Southern Hemisphere Meteorology and 
                         Oceanography, 8. (ICSHMO).",
            publisher = "American Meteorological Society (AMS)",
              address = "45 Beacon Hill Road, Boston, MA, USA",
             keywords = "trend, precipitation, ENSO, South America.",
             abstract = "During the second half of the twentieth century, in subtropical 
                         South America to the east of the Andes, rainfall trends were 
                         observed in precipitation series from local networks. The 
                         relationship of these trends with the different phases of El 
                         Niño-Southern Oscillation (ENSO) is explored in this paper. As 
                         precipitation changes are characterized by linear trends, under 
                         certain conditions, the total linear trend is the result of adding 
                         the partial linear trends corresponding to each of the ENSO 
                         phases, i.e. El Niño, La Niña and Neutral events. When splitting a 
                         series in various sub series, the linear trends of these sub 
                         series add up to the same value as the linear trend of the entire 
                         series if each of the sub series has its elements ordered in time 
                         around the same mean value and variance as the complete series. A 
                         linear trend is a special case of a linear regression slope when 
                         the independent variable is time. These conditions were 
                         approximately fulfilled during the period 1960-1999. This property 
                         permits to isolate the linear trends of any variable corresponding 
                         to each phase, and therefore, helps to highlight or discard any 
                         possible relationship between the linear trends of the variables 
                         and the ENSO phases. Annual rainfall linear trends were calculated 
                         applying a linear regression model, to each grid point of a 3ºx3º 
                         mesh between 70º 40ºW and 16º 40ºS; regression coefficients were 
                         tested for significance through a t-test. There are positive 
                         linear trends south of 22ºS and negative to the north. In the 
                         southern area, positive significant trends of 4mm/year or more can 
                         be observed, i.e. an increase in precipitation exceeding 160mm in 
                         the last 4 decades of the twenty century, which is about 30% of 
                         the initial value. These annual rainfall trends took place 
                         predominantly during the neutral phase of the ENSO. Significant 
                         values extend northward from its southern nucleus along the east 
                         side of Andes Mountains where the climate is considerably dry. In 
                         northeastern Argentina, southern Brazil and Paraguay, half of the 
                         annual rainfall trend was also positive and came from El Niño 
                         phase with a minor contribution from La Niña and the neutral 
                         phases. Indeed, in this region more than a trend there was a 
                         change in mean value after 1980, well in phase with similar 
                         changes in the ENSO indexes. On the other hand, the region of the 
                         South Atlantic Convective Zone (SACZ) has a negative trend of up 
                         to 4mm/year, which in a total of 40 years adds to almost 160mm 
                         decrease in rainfall. Here the contribution of the neutral phase 
                         predominates, but only in the core of the negative trends Almost 
                         everywhere in the region, no trends or very small ones took place 
                         during La Niña periods. Hence, in most of subtropical South 
                         America, east of the Andes, precipitation trends during the 
                         extreme phases of the ENSO constitute only a small part of the 
                         trends of the last 40 years of the twentieth century.",
  conference-location = "Foz do Igua{\c{c}}u",
      conference-year = "24-28 Apr. 2006",
             language = "en",
         organisation = "American Meteorological Society (AMS)",
                  ibi = "cptec.inpe.br/adm_conf/2005/09.14.17.25",
                  url = "http://urlib.net/ibi/cptec.inpe.br/adm_conf/2005/09.14.17.25",
           targetfile = "1513-1518.pdf",
                 type = "Understanding long-term climate variations in the SH",
        urlaccessdate = "30 jun. 2024"
}